CA1144221A - Hollow cathode lamp with improved stability alloy for the cathode - Google Patents
Hollow cathode lamp with improved stability alloy for the cathodeInfo
- Publication number
- CA1144221A CA1144221A CA000352686A CA352686A CA1144221A CA 1144221 A CA1144221 A CA 1144221A CA 000352686 A CA000352686 A CA 000352686A CA 352686 A CA352686 A CA 352686A CA 1144221 A CA1144221 A CA 1144221A
- Authority
- CA
- Canada
- Prior art keywords
- cathode
- alloy
- weight percent
- metal
- hollow
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/04—Electrodes; Screens; Shields
- H01J61/06—Main electrodes
- H01J61/09—Hollow cathodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
- H01J1/02—Main electrodes
- H01J1/025—Hollow cathodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J17/00—Gas-filled discharge tubes with solid cathode
- H01J17/02—Details
- H01J17/04—Electrodes; Screens
- H01J17/06—Cathodes
Abstract
8 48,558 ABSTRACT OF THE DISCLOSURE
A hollow cathode type light source is provided having improved operating stability by forming the cathode of an alloy of a highly reactive, unstable prime metal of interest for spectral emission, and of a chemically sta-ble, readily sputtered metal. An alloy of silver and calcium with a small amount of magnesium provides a hollow cathode device which exhibits stable operation after a mimimum warm-up time.
A hollow cathode type light source is provided having improved operating stability by forming the cathode of an alloy of a highly reactive, unstable prime metal of interest for spectral emission, and of a chemically sta-ble, readily sputtered metal. An alloy of silver and calcium with a small amount of magnesium provides a hollow cathode device which exhibits stable operation after a mimimum warm-up time.
Description
~4Z;Zl 48, 558 HOLLOW CATHODE LAMP WITH IMPROVED
STABILITY ALLOY FOR THE CATHODE
BACKGROUND OF THE INVENTI~N
The present invention relates to spectral radia-tion or light sources and more particularly to hollow 'cathode spectral light sources. Such hollow cathode light '5 sources are used to generate spectral line emission which is characteristic of the cathode material. This generated light is used in a variety of spectrophotometric chemical analysis techniques, such as atomic absorption spectros-copy, for identifying chemical samples and determining the sample material concentration.
'~The spectral light output from a hollow cathode light source is desirably stable after a short warm-up ,period to minimize testing changes during operation. For certain metallic cathode materials it is difficult to achieve stable operation without a long warm-up period which reduces the efficiency of the laboratory procedure.
For highly reactive materials such as calcium this is a particular problem. Calcium is difficult to handle and .machine because of its reactivity with air and moisture~
and is difficult to out-gas during lamp manufacture with-'out an extended seasoning process.
It has therefore been the practice to alloy cal-,~,cium and other similarly reactive metals with a stable ,;,metal such as aluminum as taught in U.S. Patent No.
-~ 25 3,183,393. It has also been the practice to include '; another metal such as magnesium in such calcium-aluminum , alloy cathodes to provide a multi-element cathode and ::.
~, ..
.,, .,, ,~.
.
2Zl l,8, 558 spec~tral emiss-ion capability.
When calcium has been alloyed with aluminum, and al~lminum an(l mclgnes-iwm, i~. has still required a long warlll-up p~liod t:o achieve a sLable spec~ral output Or less than 2% drift per 5 minute operation. It has also been necessary to repeatedly process and season such ca-thodes during the manufacturing process to achieve even this stability.
It has been known in the art to alloy silver with highly volatile cathode metals such as arsenic for the purpose of keeping the arsenic from volatilizing too rapidly from the cathode. These arsenic-silver alloy cathodes have typically employed about 40 weight percent arsenic and 60 weight percent silver.
SUMMARY OF THE INVENTION
A stable cathode metal alloy has been discovered which contains a first readily sputterable, chemical stable metal, and a second metal which provides the de-sired spectral line radiation, which second metal is readily chemically active and unstable. The first metal is selected from the group of silver, gold, rhodium, and copper. The second metal is selected from the group consisting of calcium, thallium, cadmium, antimony, bis-muth, indium, selenium, tellunium, gallium, and zinc.
This second metal is present in an amount of up to about 25 weight percent of the alloy.
A preferred alloy which has a minimum warm-up time needed to achieve stability contains about 6 weight , percent calcium, about 3 weight percent of an addition stabilizing metal magnesium, and about 91 weight percent ' silver.
BRIEF DESCRIPTION OF THE DRAWINGS
The sole figure is an elevation view, partly in section of a hollow cathode lamp which incorporates a cathode of the alloy of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention can be best understood by refer-ence to the embodiment seen in the sole figure. A hollow ., . .
,., 42Zl 3 ~l8,558 cathode lamp 10, which is a source of spectral line radia-t:ion includes a generally tubular envelope 12, a base 14 ~nt one end and a window 16 sealed to the other end. The win(low 16 is typically formed Or ultravioLet Lransmissive glass or quartz, or similar material which efficiently transmits the shorter wavelength generated spectral radia-tion, such as the calcium 4227 Angstrom line.
Electrical lead-in 18~ 20, and 22 are sealed through the glass insulating base 14. Lead-in 18 is electrically connected to the generally cylindrical cath-ode 24, which has a hollow chamber 26 at the far end. The electrical lead-in 20 and 22 are commonly electrically connected to a ring-shaped anode electrode 28 which is spaced from ~he hollow chamber end of the cathode. Elec-' 15 trical insulating tubing 30a and 30b is provided respec-tively about lead-ins 20 and 22 to prevent any electrical discharge between these lead-ins and the cathode as the : lead-ins extend toward the anode. The discharge is fur-ther confined between the anode and the hollow portion of the cathode by a pair of insulating disks 32 and 38, which are disposec~ parallel to each other in a direction trans-verse to the cathode axis. The insulating disk 32 has a central aperture 36 which is generally aligned with the hollow open end of the cathode 24, with the disk 32 mount-ed from the lead-in 20 and 22 which pass therethrough.
The disk 32 is mounted above the hollow open end of the ' cathode, generally between the ring anode 28 and the cathode 24, with the disk 32 approaching the envelope walls 12. The disk 34 is spaced from disk 32, and has a central aperture which accepts the cathode 24 there-through. Disk 38 is likewise mounted from the lead-ins 20 and 22 which extend therethrough. Disk 38 has been found ' useful to insure that the spectral light producing dis-charge is confined between the anode and the hollow por-tion of the cathode.
The cathode 24 is preferably formed of an alloy which is predominantly of a first metal which is chemical-, ly stable, readily sputtered, and has good metal working , ..
, . .
;~
11~42Zl 4 ~8,558 and casting capability. The first metal is present in anamount greater than 50 weight percent of the alloy and is selected from the group consisting of silver, copper, gold, and rhodium. The alloy contains a second metal which provides the desired spectral line radiation of interest, and which in its pure form is readily chemically active and unstable. The second metal is selected from the group consisting of calcium, thallium, cadmium, anti-mony, bismuth, indium, selenium, tellurium, gallium, and zinc. A third metal such as magnesium may be added to improve the stability of the first and second metal alloy.
When calcium is the second metal which is the source of the spectral line radiation of interest, a preferred highly stable alloy consists of 6 weight percent calcium, 3 weight percent magnesium, and 91 weight percent silver. The silver is highly stable and easily sputtered, and permits casting of a cylinder which can be machined to form the cathode hollow portion.
The alloy is typically made by mixing the indi-vidual alloy metals in an induction heated crucible, which mixing takes place after liquification of the metals.
Such heating is carrying out in an inert atmosphere. The mixed alloy is then cast as the cylindrical rod. The cathode with a hollow portion can thereafter be machined.
The calcium may be present in the alloy with silver in amounts up to about 25 weight percent, the magnesium in amounts up to about 20 weight percent, with the remainder and predominate alloy constituent being silver. Other chemically stable, easily sputtered metals which are readily alloyed and formable into alloy metal hollow cathodes include copper, gold and rhodium. When these chemically stable, easily sputtered metals are the major constituent of the alloy, the cathode hollow will continuously expose a fresh surface at a uniform rate determined by the sputtering rate of these major consti-tuents. The less stable, chemically active metal which ' generates the desired spectral line radiation is evolved as the alloy major constituent sputters.
, ~144221 S /~,558 Hollow cathode lamps made with the alloys des-crib~d here-in exhibit stable operation after a minimum of warm-up, ~ypically less t:han ~en minutes. Such lamps are not subject to the previously observed high manufacturing rejection rates occasioned by operating instabilities.
The spectral line radiation generated by a hollow cathode lamp is typically used in atomic absorption spectrophotometry. The atomic absorption instrument can have different bandpass characteristics. For a wide bandpass instrument the co-alloying metals must only include metals which have emission lines sufficiently far from the line of interest such as the 4227 ~ trff~ line of calcium. The silver and magnesium co-alloying metals meet the restriction and do not offer interfering lines near the line of interest t Thus, silver is advantageously ~ ~lG~f)'l I Llfn used with thallium, and ca~m, while a zinc-copper alloy is advantageous.
STABILITY ALLOY FOR THE CATHODE
BACKGROUND OF THE INVENTI~N
The present invention relates to spectral radia-tion or light sources and more particularly to hollow 'cathode spectral light sources. Such hollow cathode light '5 sources are used to generate spectral line emission which is characteristic of the cathode material. This generated light is used in a variety of spectrophotometric chemical analysis techniques, such as atomic absorption spectros-copy, for identifying chemical samples and determining the sample material concentration.
'~The spectral light output from a hollow cathode light source is desirably stable after a short warm-up ,period to minimize testing changes during operation. For certain metallic cathode materials it is difficult to achieve stable operation without a long warm-up period which reduces the efficiency of the laboratory procedure.
For highly reactive materials such as calcium this is a particular problem. Calcium is difficult to handle and .machine because of its reactivity with air and moisture~
and is difficult to out-gas during lamp manufacture with-'out an extended seasoning process.
It has therefore been the practice to alloy cal-,~,cium and other similarly reactive metals with a stable ,;,metal such as aluminum as taught in U.S. Patent No.
-~ 25 3,183,393. It has also been the practice to include '; another metal such as magnesium in such calcium-aluminum , alloy cathodes to provide a multi-element cathode and ::.
~, ..
.,, .,, ,~.
.
2Zl l,8, 558 spec~tral emiss-ion capability.
When calcium has been alloyed with aluminum, and al~lminum an(l mclgnes-iwm, i~. has still required a long warlll-up p~liod t:o achieve a sLable spec~ral output Or less than 2% drift per 5 minute operation. It has also been necessary to repeatedly process and season such ca-thodes during the manufacturing process to achieve even this stability.
It has been known in the art to alloy silver with highly volatile cathode metals such as arsenic for the purpose of keeping the arsenic from volatilizing too rapidly from the cathode. These arsenic-silver alloy cathodes have typically employed about 40 weight percent arsenic and 60 weight percent silver.
SUMMARY OF THE INVENTION
A stable cathode metal alloy has been discovered which contains a first readily sputterable, chemical stable metal, and a second metal which provides the de-sired spectral line radiation, which second metal is readily chemically active and unstable. The first metal is selected from the group of silver, gold, rhodium, and copper. The second metal is selected from the group consisting of calcium, thallium, cadmium, antimony, bis-muth, indium, selenium, tellunium, gallium, and zinc.
This second metal is present in an amount of up to about 25 weight percent of the alloy.
A preferred alloy which has a minimum warm-up time needed to achieve stability contains about 6 weight , percent calcium, about 3 weight percent of an addition stabilizing metal magnesium, and about 91 weight percent ' silver.
BRIEF DESCRIPTION OF THE DRAWINGS
The sole figure is an elevation view, partly in section of a hollow cathode lamp which incorporates a cathode of the alloy of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention can be best understood by refer-ence to the embodiment seen in the sole figure. A hollow ., . .
,., 42Zl 3 ~l8,558 cathode lamp 10, which is a source of spectral line radia-t:ion includes a generally tubular envelope 12, a base 14 ~nt one end and a window 16 sealed to the other end. The win(low 16 is typically formed Or ultravioLet Lransmissive glass or quartz, or similar material which efficiently transmits the shorter wavelength generated spectral radia-tion, such as the calcium 4227 Angstrom line.
Electrical lead-in 18~ 20, and 22 are sealed through the glass insulating base 14. Lead-in 18 is electrically connected to the generally cylindrical cath-ode 24, which has a hollow chamber 26 at the far end. The electrical lead-in 20 and 22 are commonly electrically connected to a ring-shaped anode electrode 28 which is spaced from ~he hollow chamber end of the cathode. Elec-' 15 trical insulating tubing 30a and 30b is provided respec-tively about lead-ins 20 and 22 to prevent any electrical discharge between these lead-ins and the cathode as the : lead-ins extend toward the anode. The discharge is fur-ther confined between the anode and the hollow portion of the cathode by a pair of insulating disks 32 and 38, which are disposec~ parallel to each other in a direction trans-verse to the cathode axis. The insulating disk 32 has a central aperture 36 which is generally aligned with the hollow open end of the cathode 24, with the disk 32 mount-ed from the lead-in 20 and 22 which pass therethrough.
The disk 32 is mounted above the hollow open end of the ' cathode, generally between the ring anode 28 and the cathode 24, with the disk 32 approaching the envelope walls 12. The disk 34 is spaced from disk 32, and has a central aperture which accepts the cathode 24 there-through. Disk 38 is likewise mounted from the lead-ins 20 and 22 which extend therethrough. Disk 38 has been found ' useful to insure that the spectral light producing dis-charge is confined between the anode and the hollow por-tion of the cathode.
The cathode 24 is preferably formed of an alloy which is predominantly of a first metal which is chemical-, ly stable, readily sputtered, and has good metal working , ..
, . .
;~
11~42Zl 4 ~8,558 and casting capability. The first metal is present in anamount greater than 50 weight percent of the alloy and is selected from the group consisting of silver, copper, gold, and rhodium. The alloy contains a second metal which provides the desired spectral line radiation of interest, and which in its pure form is readily chemically active and unstable. The second metal is selected from the group consisting of calcium, thallium, cadmium, anti-mony, bismuth, indium, selenium, tellurium, gallium, and zinc. A third metal such as magnesium may be added to improve the stability of the first and second metal alloy.
When calcium is the second metal which is the source of the spectral line radiation of interest, a preferred highly stable alloy consists of 6 weight percent calcium, 3 weight percent magnesium, and 91 weight percent silver. The silver is highly stable and easily sputtered, and permits casting of a cylinder which can be machined to form the cathode hollow portion.
The alloy is typically made by mixing the indi-vidual alloy metals in an induction heated crucible, which mixing takes place after liquification of the metals.
Such heating is carrying out in an inert atmosphere. The mixed alloy is then cast as the cylindrical rod. The cathode with a hollow portion can thereafter be machined.
The calcium may be present in the alloy with silver in amounts up to about 25 weight percent, the magnesium in amounts up to about 20 weight percent, with the remainder and predominate alloy constituent being silver. Other chemically stable, easily sputtered metals which are readily alloyed and formable into alloy metal hollow cathodes include copper, gold and rhodium. When these chemically stable, easily sputtered metals are the major constituent of the alloy, the cathode hollow will continuously expose a fresh surface at a uniform rate determined by the sputtering rate of these major consti-tuents. The less stable, chemically active metal which ' generates the desired spectral line radiation is evolved as the alloy major constituent sputters.
, ~144221 S /~,558 Hollow cathode lamps made with the alloys des-crib~d here-in exhibit stable operation after a minimum of warm-up, ~ypically less t:han ~en minutes. Such lamps are not subject to the previously observed high manufacturing rejection rates occasioned by operating instabilities.
The spectral line radiation generated by a hollow cathode lamp is typically used in atomic absorption spectrophotometry. The atomic absorption instrument can have different bandpass characteristics. For a wide bandpass instrument the co-alloying metals must only include metals which have emission lines sufficiently far from the line of interest such as the 4227 ~ trff~ line of calcium. The silver and magnesium co-alloying metals meet the restriction and do not offer interfering lines near the line of interest t Thus, silver is advantageously ~ ~lG~f)'l I Llfn used with thallium, and ca~m, while a zinc-copper alloy is advantageous.
Claims (3)
1. A spectral radiation source of the hollow cathode type comprising an anode and cathode positioned within a gas filled envelope, with the operating discharge between the anode and the cathode generating spectral radia-tion which is characteristic of the metal cathode, the im-provement wherein the metal cathode, consists of an alloy of silver which is chemically stable and readily sputtered, and calcium in an amount of up to about 25 weight percent of the alloy.
2. The spectral radiation source set forth in claim 1, wherein magnesium is included in the alloy in an amount up to 20 weight percent of the alloy.
3. The spectral radiation source set forth in claim 2,wherein the metal cathode alloy consists of about 91 weight percent silver, about 6 weight percent calcium, and about 3 weight percent magnesium.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/043,529 US4437038A (en) | 1979-05-29 | 1979-05-29 | Hollow cathode lamp with improved stability alloy for the cathode |
| US043,529 | 1979-05-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1144221A true CA1144221A (en) | 1983-04-05 |
Family
ID=21927623
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000352686A Expired CA1144221A (en) | 1979-05-29 | 1980-05-26 | Hollow cathode lamp with improved stability alloy for the cathode |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4437038A (en) |
| EP (1) | EP0020142A1 (en) |
| JP (1) | JPS55161346A (en) |
| AU (1) | AU541306B2 (en) |
| CA (1) | CA1144221A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5483121A (en) * | 1992-04-24 | 1996-01-09 | Koto Electric Co., Ltd. | Hollow cathode discharge tube |
| CN112126814A (en) * | 2019-06-25 | 2020-12-25 | 国标（北京）检验认证有限公司 | Copper-bismuth alloy for hollow cathode bismuth lamp cathode and preparation method thereof |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58223252A (en) * | 1982-06-22 | 1983-12-24 | Hamamatsu Tv Kk | Light source lamp |
| GB2145557B (en) * | 1983-08-13 | 1987-05-07 | Emi Plc Thorn | Improvements in discharge lamps |
| ITMI20012389A1 (en) * | 2001-11-12 | 2003-05-12 | Getters Spa | CABLE CATHODE WITH INTEGRATED GETTER FOR DISCHARGE LAMPS AND METHODS FOR ITS REALIZATION |
| ITMI20032208A1 (en) * | 2003-11-14 | 2005-05-15 | Getters Spa | CATODO WITH INTEGRATED AND LOW FUNCTION GETTER WORK FOR COLD CATO LAMPS. |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3183393A (en) * | 1962-04-20 | 1965-05-11 | Westinghouse Electric Corp | Discharge device |
| JPS503390A (en) * | 1973-05-11 | 1975-01-14 | ||
| JPS5398780U (en) * | 1977-01-14 | 1978-08-10 |
-
1979
- 1979-05-29 US US06/043,529 patent/US4437038A/en not_active Expired - Lifetime
-
1980
- 1980-05-23 AU AU58698/80A patent/AU541306B2/en not_active Expired
- 1980-05-26 CA CA000352686A patent/CA1144221A/en not_active Expired
- 1980-05-29 JP JP7091380A patent/JPS55161346A/en active Granted
- 1980-05-29 EP EP80301777A patent/EP0020142A1/en not_active Ceased
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5483121A (en) * | 1992-04-24 | 1996-01-09 | Koto Electric Co., Ltd. | Hollow cathode discharge tube |
| CN112126814A (en) * | 2019-06-25 | 2020-12-25 | 国标（北京）检验认证有限公司 | Copper-bismuth alloy for hollow cathode bismuth lamp cathode and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS55161346A (en) | 1980-12-15 |
| AU5869880A (en) | 1980-12-04 |
| JPH0131266B2 (en) | 1989-06-23 |
| EP0020142A1 (en) | 1980-12-10 |
| US4437038A (en) | 1984-03-13 |
| AU541306B2 (en) | 1985-01-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |